Liquid crystal display devices, having the advantages of no radiation, light and power saving, have been widely used in a variety of information, communications, consumer electronics products. The liquid crystal display device generally includes a display panel including an array substrate and a color film substrate disposed opposite to each other, and a liquid crystal layer disposed between the two substrates. The array substrate includes a scanning line and a data line, and the scanning line and the data line are insulated from each other to define a plurality of sub-pixels. Each of the sub-pixels includes a pixel electrode, a common electrode and a thin film transistor, and the pixel electrode is electrically connected to a drain of the thin film transistor. When being displayed, the thin film transistor connected to the scanning line is turned on by applying a scanning signal to the scanning line, and the data voltage applied to the data line charges the pixel electrode through the thin film transistor that is turned on such that an electric field is formed between the pixel electrode and the common electrode so as to drive the liquid crystal to rotate, thereby achieving the display of image.
With the continuous development of the display technology, the demands for high PPI (Pixels Per Inch, the number of pixels per inch), and even ultra-high PPI become increasingly higher.
However, with the continuous improvements of PPI in a display panel, pixel arrangements become denser, sizes of each sub-pixel are getting smaller, which not only present great challenges to the device design of the display panel, but also cause a lot of problems, for example, the pixel aperture ratios, which refers to a ratio between a area of the light passing through portion except for the wiring part and transistor part (Usually being hidden by the black matrix) of each of the sub-pixels and a whole area of each of the sub-pixels, are limited by process technology constraints such as the line width and spacing limits between ever-smaller adjacent sub-pixels, when a stable light exposure in the lithography process can not be achieved, thereby resulting in a poor exposure in a display panel. The higher the opening ratio is, the hither the efficiency of light passes.